A thermoelectric device comprises two fluid circuits (a warm circuit and a cold circuit) between which are placed the thermoelectric elements (also referred to here as "thermoelements" for shorthand purposes), with at least one of these fluid circuits being a liquid circuit using parallel tubular pipes assembled in a stacked arrangement.
According to a known device, the thermoelements are placed in contact with tubular heat exchangers disposed in alternate layers in which warm and cold fluids flow, these layers being stacked one above the other and secured together to provide an assembly.
The present invention is concerned with providing a tight coupling assembly or joint for tubular elbows connected to the extremities of the tubes of the same layer of heat exchangers (containing the same warm or cold fluid) or between different layers for the same fluid, i.e., between two layers for warm fluid or two layers for cold fluid.
The problem of joining such elbows and other fluid connections to the layers of heat exchangers is difficult to solve.
It can be solved by brazing or welding of the elbows on the extremities of the heat exchanger tubes of the assembly.
Nevertheless, a joint provided by brazing or welding dictates that the brazing or welding operation is feasible using materials (metal tubes and elbows, and a filler metal solder) which are acceptable for the operating conditions (i.e, factors such as stability, corrosion by the fluids, toxicity and the like). Sometimes special welding is required for some metals like stainless steels. In either case, providing such a connection is a delicate operation because the heat exchanger assembly is compact and the tubes are arranged with the minimum possible spacing. Very little space is thus available for brazing or welding, and a perfectly tight weld must be provided around the entire periphery of a tubular section. Moreover, the heating of the tubular members attendant such a welding or brazing operation can damage components of the thermoelectric device, this heat being transferred by conduction along the heat exchanger tubes to the basic assembly.
It has been proposed to provide, by brazing, connection of the components of a layer to a counterplate secured by screws or bolts on the end plate itself. It will be understood that the connections between layers of the same kind (cold or warm) must be adjusted because of expansion and contraction of the layers of the same kind (cold or warm) after the counterplate is in place, and to this end, screws or bolts must be disposed at accessible places for tightening the connections. Such adjustments are very difficult for connecting elbows in the same layer. Another disadvantage is the trend toward curvature of the counterplates where the hydraulic connections are brazed, which can require adjustment of the support surface in order to obtain the required tightness of the joint. Moreover, this adjustment requires the presence of a toric ring seal disposed in a groove provided in either the end plate or the counterplate.